The pharmaceutical industry spends billions of dollars each year on direct-to-consumer advertising (DTCA) of prescription drugs. Because of the challenge of conveying health information to the public and the potential for unintended consequences, the merits of DTCA have been subject to considerable debate. Although several studies have examined the effect of DTCA on consumers' behavior and health outcomes, most have used aggregate spending, rather than more refined measures of ad exposure, and most have quantified the impact of DTCA regarding a single drug or therapeutic class. This is important because there are significant differences in the patient population, severity, chronicity, and symptomatology of conditions treated by commonly advertised drugs, and these differences may influence the effect of DTCA. In addition, few investigations have examined how patient or regional health system characteristics moderate the impact of direct-to-consumer advertising, yet both economic and behavioral theory suggest that such factors may have an important influence on its effects. There is also important variation in the content of ads, and work from other areas of health communication suggest that this content influences how consumers respond to health information, yet few analyses have assessed how qualitative and executional characteristics of DTCA may influence its effects. We propose a series of interrelated aims that capitalize on a unique combination of health care utilization data, derived from one of the largest collections of health plan insurance claims available, with measures of exposure to television ads derived from Nielson Media Research. We will supplement this information with data from the Area Resource Files and IMS Health to derive information regarding the context in which the advertising takes place. We will also develop and apply a set of codes capturing key qualitative and executional ad characteristics. The combination of these data will allow us to examine the effects of DTCA on health care utilization and pharmaceutical sales across therapeutic classes, and to explore the interaction of individual characteristics, contextual influences, and ad characteristics on the relationship between DTCA and utilization and sales. With expertise in the study of advertising and health behavior as well as pharmacoepidemiology and pharmaceutical policy, our team is highly qualified to perform the proposed research. We will use advanced econometric techniques and our analyses will yield important information for policymakers and other stakeholders seeking to optimally balance the complex risks and benefits of direct-to-consumer advertising.